Particle Image Velocimetry – Particle Density and Neutral Buoyancy

Density of particle vs. density of fluid:

Silver Metal Coated Hollow Glass Microspheres

Many flow visualizations are done in water but there are a variety of other liquids and even water based solutions that will have differing densities whose velocity fields are being mapped or will be in the future. Therefore, having seed particles to match these differing densities is important to provide neutral buoyancy, one of the most important factors regarding flow conformity.

With polyethylene spheres contributing a range of densities that provide neutrally buoyant tracers for most water fluid flows thought needs to be directed towards furnishing tracers to match other densities. Gasoline and similar carbon based fluids are an example of areas of fluid flow mechanics where lower density tracer particles are necessary. Silver Coated Hollow Glass Microspheres have the density range to potentially work for many carbon chain liquids, with current densities ranging from .15 g/cc to .75 g/cc and possibly higher. This leaves some room for improvement in the densities between .75 g/cc and .96 g/cc.

There are many options available for neutrally buoyant microspheres in water. While, other fluids may have more difficulty finding an ideal density tracer, there are options available and scientists are working to provide more unique and targeted tracer particles for use with low density fluids.

Neutrally Buoyant in Water – Microspheres with Specific Gravity of 1g/cc

Cospheric offers polymer microspheres with specific gravity of 1g/cc are specifically designed to match the density of water for optimal suspension of particles. Suspension of microspheres in water enables the visualization and characterization of fluid flow and testing the capability of devices to withstand particulate matter in the fluid stream, ensuring that microspheres do not settle and do not float on the surface. Most of these polymer microspheres are at least moderately opaque and clearly visible in water, clear or translucent liquids.